Take the dark stuff from the streaks and pan it down. Use a magnet to see if any of the black material jumps to a magnet. If it does, you've at least found super-heavies. Super-heavies, that's where gold likes to hide. (If it's coal, it won't be attracted to a magnet either.)
If none of the black material jumps to a magnet, you may be looking at rotting organic material (or coal). Plus, when you try to pan it, the material will be very light, and it will wash out of the pan very quickly.
What's the history of gold in your area? Is it micron/flour gold? Or, is it flakes and chunks?
Research will be a key, and perhaps you've already done a lot, if not, look up everything you can find in your area about gold accumulations and gold recovery.
If you're in Georgia, you should be able to find some material to help narrow your search as Georgia's gold history goes back quite a ways.
All the best,
Lanny
http://www.treasurenet.com/forums/metal-detecting-gold/69-bedrock-gold-mysteries.html